云南蔷薇属部分种质资源对白粉病的抗性鉴定

对14个云南蔷薇属种质资源（包括7个栽培品种和7个野生种）进行白粉病抗性的离体鉴定和田间鉴定,其中免疫品种（种）2个,中抗品种（种）8个,中感品种1个,高感品种（种）3个。白粉病离体鉴定与田间鉴定两种方法的抗性评价结果完全一致,表明该方法可作为白粉病抗性快速鉴定的方法。     

Seed treatment for the control of Sphaerotheca fuliginea in muskmelon seedlings

The effects of powdery mildew (caused by Sphaerotheca fuliginea )on muskmelon seedlings and the efficacy of seed treatment with systemic fungicides were examined under controlled environmental conditions. The fresh weight of seedlings infected with powdery mildew was substantially less than that of uninoculated seedlings 5 weeks after inoculation, and the inoculated seedlings shrivelled 1 week later. The fungicides fenarimol and triadimenol applied to the seeds did not affect germination and suppressed powdery mildew effectively when applied at a rate equivalent to 8 g fungicide product per kg seed. Under conditions moderately conducive to the pathogen, fenarimol markedly reduced disease severity and its effect when applied as a seed treatment was as effective as foliar treatment. When conditions were highly conducive to the pathogen, seed treatment with fenarimol was not effective. Development of powdery mildew and efficacy of the seed treatments were related to soil type: disease developed earlier and more intensely on seedlings grown in sandy soil than those in organic medium, and seed treatment had a more pronounced effect on seedlings grown in sandy soil. The results indicate that fungicidal treatment of muskmelon seeds may offer an adequate means of reducing powdery mildew infections on seedlings.     

Effect of aerated compost tea on grapevine powdery mildew, botrytis bunch rot and microbial abundance on leaves

Aerated compost tea (ACT), prepared from immature compost, was applied to foliage and fruit of grapevines (Vitis vinifera) to assess its potential for suppressing two important diseases: botrytis bunch rot, caused by Botrytis cinerea, and powdery mildew, caused by Erysiphe necator. An ACT applied to leaves of Cabernet Sauvignon vines in pots 7 days before inoculation with E. necator conidia reduced mean powdery mildew severity on the three youngest expanded leaves (at inoculation) to less than 1 %; mean severity on non-treated, inoculated leaves was 15 %. Multiple applications of ACTs at two vineyards in different growing seasons suppressed powdery mildew to <1 % mean severity on Chardonnay leaves (non-treated 79 % severity) and bunches (non-treated 77 % severity), and on Riesling leaves (non-treated 24 % severity). The same treatments reduced the incidence of Chardonnay bunches with latent B. cinerea and Riesling bunches with sporulating B. cinerea, although the level of botrytis bunch rot in both experiments was not economically damaging. The numbers of culturable bacteria, fungi and yeasts on Chardonnay leaves were higher than pre-treatment levels 10 days after ACT application, as were fungal numbers on Riesling leaves 21 days after treatment. Suppression by ACTs of two fruit and foliar pathogens of grapevine with different biology and epidemiology indicated potential for their use as a tactic in integrated disease management. Further testing of ACTs in a range of viticultural environments and application regimes will contribute to a better understanding of the impact of this tactic on disease, grape and wine quality.     

苦瓜白粉病病原菌和生理小种的鉴定及苦瓜对白粉病的抗性遗传分析

为明确海南省苦瓜白粉病的病原菌、生理小种及苦瓜对白粉病的抗性遗传规律,结合形态学鉴定和分子鉴定解析白粉病菌及生理小种种类,通过显微镜观察白粉病菌侵染过程,并应用主基因+多基因混合遗传模型分析法探讨苦瓜对白粉病的主要抗性遗传规律。结果表明:采集自海南省6个市(县)的苦瓜白粉病病原菌均为单囊壳白粉菌Sphaerotheca fuliginea,属生理小种2F,该菌在侵染苦瓜叶片时有4个关键时期:接种后4 h为分生孢子萌发高峰期,8 h为附着孢形成高峰期,16～24 h为次生菌丝形成高峰期,5 d为分生孢子梗形成高峰期。将其接种于苦瓜抗、感品系,对白粉病的抗性符合2对加性-显性-上位性主基因+加性-显性多基因模型,主基因和多基因共同控制苦瓜对白粉病的抗性,其中以主基因遗传为主,且会受到环境变异的影响。根据苦瓜抗性遗传规律,F2代主基因遗传率最高,受环境影响最小,在苦瓜的白粉病抗性育种中,以早期世代F2代作为有效选择世代。研究表明白粉病菌侵染叶片的前2 d是白粉病防治的最佳时期,所以在白粉病易发的物候期,可将防治时间提前1～2 d。     

Polygenic powdery mildew disease resistance in Arabidopsis thaliana: quantitative trait analysis of the accession Warschau-1

To further the understanding of the natural genetic diversity for disease resistance to powdery mildew ( Erysiphe cichoracearum ) in Arabidopsis thaliana , quantitative trait loci analysis was undertaken on recombinant inbred lines derived from a cross between the resistant accession Warschau-1 and the susceptible Columbia-0. Powdery mildew grew less well on Warschau-1, but the resistance was not associated with a specific block in the infection sequence. Two potential powdery mildew disease-resistance loci were identified and mapped, one with a major effect and one with a minor effect on disease resistance. The two loci acted in an additive manner to confer resistance, and together they explained 65% of the variation in resistance. In addition, the major powdery mildew disease-resistance locus was genetically mapped to the bottom of chromosome III, a region containing the powdery mildew resistance loci RPW7 , RPW8 and RPW10 . Unlike resistance mediated by the RPW8 locus in the accession Moscow-1, resistance in Warschau-1 was not correlated with the hypersensitive response, highlighting the influence of genetic background or environmental factors on the expression of disease resistance. Together with the powdery mildew resistance loci described in other studies, these results suggest that A. thaliana is a useful source of natural powdery mildew disease resistance, which potentially can be utilized in fundamental studies and as a tool for applied studies.     

Variation in severity of cashew powdery mildew (Oidium anacardii Noack) disease in Tanzania: Implications for research and extension

Abstract

Cashew trees in farmers’ fields in two contrasting areas in southern Tanzania were surveyed for growth, powdery mildew development, amounts and applications of sulphur, pest damage and nut yield by village‐based extension workers in 1993. There was a wide range of powdery mildew levels on cashew flowers, apples and nuts at both the Tunduru (inland) and Newala (western Makonde plateau). In both Newala and Tunduru application of sulphur dust was associated with reduced severity of blossom powdery mildew. Sulphur usage commenced later in Newala than Tunduru though this was associated with earlier onset of blossoming in the latter district. Farmers in both areas applied similar numbers of rounds of sulphur, however in Newala more sulphur was applied per tree reflecting the bigger trees found in this district. There was a highly significant (P < 0.001) negative association between use of sulphur and severity of blossom powdery mildew irrespective of nut yield. There was a strong positive association (P < 0.01) between use of sulphur and more than one nut per panicle from harvests in October, no significant association in November and a significant negative association (P < 0.05) between use of sulphur and more than one nut per panicle in December. The survey highlighted areas in Newala where there were higher powdery mildew levels, through either lack of sulphur application or poor control by late application of sulphur, with relatively high numbers of nuts per panicle. Conversely, areas were identified where despite control of cashew powdery mildew severity by application of sulphur nut yield remained relatively low. The results suggest that final yield results from an interaction of factors of which cashew powdery mildew is only one. There was a highly significant (P < 0.01) association between the number of sulphur rounds and severity of cashew powdery mildew (Newala data only) but no significant association between number of rounds of sulphur and yield taken during October. Pest damage estimates from cashew nuts showed no consistent pattern in either region. Survey results suggest that there is considerable potential in the optimization of sulphur usage as a strategy for control of powdery mildew.     

The effects of low-volume aeration on the residues and biological effectiveness of chlorpyrifos-methyl applied to wheat

The effects of low-volume ventilation on the persistence and biological efficacy of chlorpyrifos-methyl applied to English wheat were investigated. Four 20-tonne batches of wheat were treated with a dose of 2.5 mg kg^?1 chlorpyrifos-methyl. After treatment, two of the batches were aerated continuously at a rate of 17 m³ h^?1 tonne^?1 (10 cfm tonne^?1) for 16 weeks. The remaining two batches were not aerated. Samples were collected from both aerated and non-aerated wheat at intervals over the 16-week storage period and subjected to biological assay using laboratory multi-organophosphorus-resistant strains of Tribolium castaneum, Sitophilus granarius, Sitophilus oryzae and Oryzaephilus surinamensis. The samples were also analysed for chlorpyrifos-methyl residues. No differences in either the biological efficacy or the rate of chemical decomposition were detected between the aerated and non-aerated wheat.     

Comparison of resistance-inducing abilities of virulent and avirulent races of Erysiphe graminis f.sp. hordei and a race of Erysiphe graminis f.sp. tritici in barley

Resistance to powdery mildew was induced in barley by preinoculation with virulent and avirulent races of barley powdery mildew ( Erysiphe graminis f.sp. hordei ), and with a race of wheat powdery mildew ( E. graminis f.sp. tritici ). Four inducer densities were tested in 13 different induction periods between 1 and 24 h. Generally, the resistance induced by barley powdery mildew increased up to 10-12 h of induction and was maintained in longer induction periods. The inducing abilities of virulent and avirulent races could not be distinguished up to 10-12 h of induction, after which the inducing ability of avirulent races increased significantly in relation to virulent races. Wheat powdery mildew was able to induce more resistance than barley powdery mildew in induction periods up to 8 h. In a single inoculation procedure the number of haustoria developing from virulent barley powdery mildew decreased as inoculum density increased. The effect was ascribed to induction of resistance. This reduction of infection efficiency in the compatible interaction was compared to induced resistance. However, the inoculum density needed for 50% resistance induction in the double inoculation procedure was approximately 40 times higher than the inoculum density needed for 50% reduction in infection efficiency in the single inoculation procedure.     

Effects of Temperature on the Length of the Incubation Period of Rose Powdery Mildew (Sphaerotheca pannosa var. rosae)

The effect of temperature on the length of the incubation period of rose powdery mildew, caused by Sphaerotheca pannosa var. rosae, was studied. At constant temperature over the range 8–28°C, the length of the incubation period ranged from 3 to 10 days; no visible colonies developed at 30°C after 19 days. The relationship between temperature and the rate of development of mildew colonies within the incubation period under constant temperature was described by two alternative non-linear models (exponential and thermodynamic). The resulting curves were asymmetrically bell-shaped with an optimum temperature of c. 23°C. The two constant-temperature models predicted the development of powdery mildew under fluctuating temperatures with similar accuracy, even though the exponential model fitted the constant temperature data less well than the thermodynamic model. The thermodynamic model failed to fit the fluctuating-temperature data directly, whereas the exponential model fitted those data directly and the fit was similar to the corresponding model from the constant-temperature data. Fitting the models to the combined (constant and fluctuating temperature) data gave results that were nearly identical to those based on the constant-temperature data alone.     

Compost Tea as a Container Medium Drench for Suppressing Seedling Damping-Off Caused by Pythium ultimum

ABSTRACT Compost tea is being used increasingly in agricultural production to control plant diseases. However, there has been limited investigation relating disease control efficacy to various compost tea production methods, particularly compost tea produced with active aeration and additives to increase microbial population densities in compost tea. Aerated compost tea (ACT) and nonaerated compost tea (NCT), produced with or without additives, was investigated for the suppression of damping-off of cucumber caused by Pythium ultimum. Compost tea was used to drench soilless container medium inoculated with P. ultimum; effect on damping-off ranged from not suppressive to consistently suppressive depending on the method used to produce the tea. The most consistent formulation for damping-off suppression was ACT produced with kelp and humic acid additives. Producing ACT with a molasses-based additive inconsistently suppressed damping-off; evidence suggests that residual nutrients can interfere with disease suppression. Heating or diluting compost tea negated suppression. Across all compost tea samples, there was no significant relationship of bacterial populations, measured as active cells, total cells, or CFU, to disease suppression. However, for all ACT produced without the molasses-based additive, there was a threshold of bacterial population density (6 log(10) active cells per ml, 7.48 log(10) total cells per ml, or 7 log(10) CFU per ml) above which compost teas were suppressive.     

Biological evaluation of neopeptins isolated from a Streptomyces strain

BACKGROUND: Microbial secondary metabolites are a rich source of antifungal agents and have merit as alternatives to synthetic fungicides. To develop disease control agents against powdery mildew, the lipopeptide antibiotic neopeptins were identified from the culture broth of a Streptomyces sp., and in vivo control efficacy of the compounds was evaluated on cucumber plants under glasshouse conditions. RESULTS: The Streptomyces sp. KNF2047 antagonistic against powdery mildew development in cucumber plants was isolated from a soil sample. Antifungal compounds were purified from the culture broth and identified as neopeptin A and B. In vitro microtitre assays revealed the inhibitory activities of the compounds in the range 128-512 microg mL(-1) against the mycelial growth of Alternaria mali, Botrytis cinerea, Cladosporium cucumerinum, Colletotrichum lagenarium, Didimella bryoniae and Magnaporthe grisea. Although neither compound showed remarkable in vitro antifungal activity against other plant pathogenic fungi, a mixture of neopeptins (484 mg of neopeptin A and 290 mg of neopeptin B per gram of partially purified powder) showed potent protective and curative activity against cucumber powdery mildew in vivo. The disease control activity of the neopeptins at a concentration of 2.4 mg L(-1) was 92.1%, which was similar to that of the commercial fungicide fenarimol (89.3% at 63 mg L(-1)) and that of the commercial biocontrol agent Actinovate (67.4% at 2 x 10(7) cfu L(-1)). CONCLUSION: Neopeptin mixtures isolated from Streptomyces sp. KNF2047 showed potent disease control activity against powdery mildew development on cucumber plants. .     

Nitrogen-induced changes in colony density and spore production of Erysiphe graminis f.sp. hordei on seedlings of six spring barley cultivars

The influence of increasing nitrogen supply (30, 60, 120 and 240 mg N per pot) on susceptibility was studied on seedlings of six cultivars of spring barley inoculated with virulent isolates of powdery mildew. The colony density (CD) measured as colonies per cm² was significantly increased with increasing application of nitrogen on all cultivars, and a significant interaction was found between N and cultivar. The different reactions of the cultivars could not be ascribed to lack of N uptake. In general, increasing N application enhanced the sporulation capacity of colonies (CSC) irrespective of increased CD and the cumulative production of spores per cm² leaf (CSCM) increased strongly with N application in all cultivars. No interaction between N and cultivar was found for the latter component. The increase in CSCM closely corresponded with the increase in N content and fresh weight of uninoculated leaves. No interaction between N treatment and powdery mildew isolates was found for infection efficiency and spore production per colony, when tested on one cultivar. The N-induced changes in infection and sporulation can explain the main part of the increasing effect of N fertilization on powdery mildew development in the field. The results indicate that it may be possible to breed for or select barley cultivars with low N impact on powdery mildew development.     

陇南山区小麦白粉病流行程度预测模型

调查分析1990~2005年陇南山区小麦白粉病发生、流行资料,发现:陇南白龙江流域为小麦白粉病常发重发生区,徽成盆地为小麦白粉病易发区,西汉水流域为小麦白粉病轻发区;小麦感病品种面积、上年秋苗平均病叶率和病田率、当年早春平均病田率、上年7、10月和当年5月平均气温、当年4月和上年7、8、11月降水量与全市春季小麦白粉病流行程度相关十分显著,上年9月到次年3月平均气温和4~8月降水量与小麦白粉病流行程度呈正相关,4~8月平均气温和9月到次年3月降水量与小麦白粉病流行程度呈反相关。由此建立的预报模型,历史拟合率可达93.75%,2006年业务应用预报准确率100%。     

Weed infestation and tea growth under various weed management methods in a young tea (Camellia sinensis[L.] Kuntze) plantation

A field experiment was conducted in the low country of Sri Lanka, during the period 1994–1995 to investigate the severity of weed infestation and tea growth in relation to weed management methods in newly established tea ( Camellia sinensis [L.] Kuntze). Manual weeding (hand and slash weeding) at various intervals was compared with various herbicides, with or without mulching. Weed control with herbicides was superior to that of hand weeding at 6-week intervals or more. Weed control with oxyfluorfen at 0.29 kg ai ha⁻¹ + paraquat at 0.17 kg ai ha⁻¹ or glyphosate at 0.99 kg ai ha⁻¹ + kaolin at 3.42 kg ha⁻¹ were superior. Plots unweeded for 12 weeks or more produced significantly greater ( P  < 0.05) weed biomass than plots unweeded for 6 weeks. Although the least weed dry weight ( P  < 0.05) and the greatest number of weed species were recorded with hand weeding at 2 week intervals, there was no particular benefit on tea growth when compared with hand weeding at 6 and 12 week intervals. Inter row mulching in chemically treated plots was more favorable for tea growth than no mulching, while living weed cover in unmulched slash weeded plots suppressed tea growth. A combination of mulching and herbicides, particularly oxyfluorfen and paraquat, followed by hand weeding at least every 6–8 weeks was considered the most appropriate weed management system for young tea.     

Residual effects of triadimefon in soil on powdery mildew and yield of spring barley

Residual triadimefon (or a breakdown product), from a spray application (2 kg/ha) to field soil in 1978, significantly decreased powdery mildew on spring barley throughout two subsequent growing seasons, with consequent yield increases of 42% in 1980 and 18% in 1981.
In other field experiments triadimefon applied to soil at rates >0.06 kg/ha decreased mildew in barley growing in the soil 11 months later. In these experiments triadimefon, but not benomyl, imazalil or prochloraz (all at 0.5 kg/ha) significantly decreased mildew up to harvest and increased yield by 22%.
Triadimefon incorporated into a loam soil and a peat-based compost at rates >0.1 ng/g significantly decreased mildew on barley grown in pots under glasshouse conditions. Plants grown in the treated compost at the same time but in isolated pots supplied with filtered moistened air and capillary watering required more triadimefon (>100 ng/g) in soil for significant mildew control.
Despite strong adsorption of triadimefon to soil (Kd 19.4), an active substance appears to remain available for uptake and translocation by barley plants over long periods. The sensitivity of barley mildew to extremely small residues of triadimefon is discussed in relation to the siting of field experiments on mildew control. The implications for widespread commercial use of formulations containing triadimefon are discussed in relation to disease control practice in cereal growing systems.     

普通小麦“兰考90(6)”品系对白粉病抗性的遗传研究

 普通小麦(Triticum aestivum L.)"兰考90(6)"系列品系是以六倍体小黑麦(X Triticosecale Wittmack;AABBRR)为白粉病抗源培育的新的小麦-黑麦1BL/1RS异易位系。这些品系高抗白粉病。小麦白粉病抗性基因推导试验证明,"豫麦66"携带的抗病基因与大多数已经报道的小麦抗白粉病基因不同。用白粉菌[Blumeria graminis (DC.) E. O. Speer f. sp. tritici]单孢堆分离物进行的遗传分析表明,"兰考90(6)"品系携带一个小种专化的隐性抗白粉病基因。对"中国春"和"兰考90(6)21-12"杂交F₂分离群体进行1RS染色体检测,结果证明该抗白粉病基因不在1RS染色体臂上。本研究为有效利用"兰考90(6)"系列品系中的抗白粉病基因提供了科学依据。     

特谱唑防治小麦白粉病研究

特谱唑对小麦白粉病效果优异，用药量低，持效期长，内吸传导性能强，使用安全，而且比目前常用的高效药剂粉锈宁效果更好，剂量更少。温室测定结果表明，特谱唑对白粉病菌的毒力和粉锈宁更强，其ＥＣ５０的毒力指数（以粉锈宁为１００），治疗作用的为５７３，保护作用的为２０９６；具有较强的内吸向上传导性能，采用喷雾法，在施药后长成的第１叶片（即第２叶）可保持很高的药效，而长成的第２叶片的效果则明显下降。田间试验和示     

Molecular phylogeny reveals phenotypic evolution of powdery mildews (Erysiphales, Ascomycota)

Powdery mildew fungi, comprising 16 genera and ca. 900 species, are exclusively obligate biotrophs of plants. Although several publications have addressed the phylogeny and evolution of powdery mildews based on morphology and host relationships, this review focuses on the evolution of several phenotypic characters based on molecular phylogeny: (1) morphology of appendages; (2) mycelium, ectoparasitic or endoparasitic; (3) number of asci per chasmothecium (fruiting body of powdery mildews), e.g., one to several; (4) conidiogenesis, conidia catenescent (i.e., maturing in chains: Euoidium-type) or maturing one at a time (Pseudoidium-type). Putative ancestral features of the powdery mildews are described as follows. In teleomorphs, large-sized chasmothecia, containing many 8-spored asci, had many appendages with uncinate-circinate apices, arising around the supraequatorial part of chasmothecia. In anamorphs, conidia were produced in chains (Euoidium-type) without distinct fibrosin bodies. Parasitism was ectoparasitic.     

Resistance to Sphaerotheca pannosa in roses induced by 2,6-dichloroisonicotinic acid

The susceptible rose cv. Madelon and the partially resistant cv. Sonia both responded with reduced development of rose powdery mildew when they were treated with the synthetic inducer 2,6-dichloroisonicotinic acid (INA). The EC₅₀ for number of colonies cm⁻² was approximately 0.4 mg L⁻¹ in both cultivars when treated 4 days prior to inoculation. However, conspicuous differences were observed with respect to number of spores per cm². For sporulation, the EC₅₀ was 0.37 mg L⁻¹ in cv. Madelon and only 0.08 mg L⁻¹ in cv. Sonia. A comparison with the pathosystems cucumber/ Sphaerotheca fuliginea and red cabbage/ Peronospora parasitica is made and the importance of the observed phenomenon for the selection of parents in a breeding programme for (partial) resistance is discussed.